Mineral wool quality test



Dec. 14, 1965 J. E. GASTON 3,222,924

MINERAL WOOL QUALITY TEST Filed Feb. 6, 1963 MINERAL WOOL FORM AQUEOUS CLAY DISPERSION WATER PASS TO HEA D BOX PASS TO DRAINAGE WIRE MEASURE BOTH VOLUME AND LENGTH OF RETAINED MAT IN V EN TOR.

JACK E- GASTON United States Patent ()fifice 3,222,924 Patented Dec. 14, 1965 3,222,924 MINERAL WOOL QUALITY TEST Jack E. Gaston, Manheim Township, Lancaster County, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Filed Feb. 6, 1963, Ser. No. 256,633 4 Claims. (Cl. 73159) This invention relates generally to a mineral wool quality test, and more particularly to a method of determining the suitability of mineral wool for use in boardmaking operations. The invention also relates to the test apparatus.

Mineral wool is made by melting slag, usually iron blast furnace slag, and attenuating the melt into fibers using steam, air, mechanical spinners, or combinations of these methods. The resulting fiber diameter, fiber length, fiber strength, brittleness, softness, shot content, slug content, ratio of fine fibers to coarse fibers, color, and chemical resistance are a function of the chemical composition of the melt, the temperature of fiber formation, and this technics of attenuation. Many variables can and do enter into the process of making mineral wool, hence the product is subject to a wide variation in properties.

Mineral wool is the major ingredient in many boardmaking processes wherein the resulting boards are further processed to produce acoustical tile, insulating boards, and other structural elements. The Wet process board-making operations themselves primarily utilize a slurry of mineral wool fibers, binders, fillers, and sizes uniformly fed over a drainage wire, such as a Fourdrinier wire, which retains the mineral wool fibers and other ingredients while allowing the water to pass on through. Hence the wet bulking properties and drainage characteristics of the mineral wood fibers are exceedingly important in these board-making processes.

Mineral wool, to be of high quality, should not be dusty or full of sharp, coarse fibers. The fibers should not be brittle, soft or mushy, and the mass of fibers should not be composed of fibers which are too long, too short, or of too great a variation in diameter. The fibers should not contain too much coarse shot or slugs. These factors correlate with board production. A high quality mineral wool causes no trouble in the handling and mixing operations of the board-making procedure, it disperses easily in the mixing tank, flows smoothly through the various lines and valves, spreads evenly over the forming screen, drains readily, vacuums to a fairly smooth sheet that is thick enough at the chosen weight per square foot of screen surface to be compressed adequately in the press section, dries Without excessive shrinkage thus preventing thin board formation, and contains a sufliciently small shot or slug content to prevent scratch marks or edge damage in the finishing operation. A wool showing good volume and short length of mat in the present test correlates well with these high performance characteristics on the board-making lines.

In the past, a number of test methods have been employed to measure different properties of mineral wool, with the over-all quality being judged by how well the samples met the requirements of the numerous tests. It was possible, however, for a mineral wool to meet the requirements of the tests yet give rather unsatisfactory performance on the board-making production line. Thus there is a need for a simple test procedure which evaluates the quality of a mineral wool with respect to practically all the variables that exist insofar as these variables affect the drainage and wet bulking characteristics of the mineral wool.

It is the primary object of the present invention to supply such a test. It is a further object of the present invention to supply a simple and etficient test which may be quickly and easily made on a mineral wool sample and which nevertheless establishes a reliable correlation with production line performance.

These objects have been met in a surprisingly straight- [forward and effective manner. The invention contemplates forming an aqueous dispersion of equal parts by weight of kaolin clay and the mineral wool to be tested. The dispersion is passed to a head box, and from the head box it is then passed to a drainage wire adapted to retain the fibers and at least a portion of the clay (depending upon the characteristics of the mineral wool) while allowing the water to pass through. The test is completed by the simple step of measuring both the volume and the length of the mat of the retained clay and fibers on the wire. The greater the volume and the shorter the length of the mat, the better the quality of the mineral wool for the board-making processes.

In the drawings,

FIG. 1 represents a simplified flow diagram of the process of the present invention, and

FIG. 2 represents a simplified from of apparatus in which the mineral wool quality test may be carried out.

The mineral wool is to be slurried in water. The test should not be carried out on the mineral wool-water slurry alone since the differences between various mineral wools as to resistance to drainage and wet packing are not readily apparent unless the binders and fillers normally used in the board-making process are present in the slurry or some material that can induce a similar type of resistance to drainage is purposely added. By utilizing a clay of the kaolin type added in an amount equal to the weight of the mineral wool, the differences between the various mineral wools are emphasized and become easily detectable in the present process. The use of a standard clay to provide this resistance to drainage eliminates all variables in the test except the quality of the mineral wool. The consistency of the clayfibers mixture in the slurry will be generally in the range of 35%. In nearly all tests heretofore performed on mineral wool to check its quality by measuring fiber diameter, fiber length, shot content, brittleness, softness, chemical composition, fiber strength, etc., the sample size has ranged from a few fibers to a few grams. With such small samples, there has always been a question of how truly representative the samples could be expected to be. In this new test method, the size of sample is one-half pound, to be blended with one-half pound of clay, the whole dispersed in four gallons of water. A larger or smaller quantity could be used in the same general proportions but one-half pound of wool, one-half pound of clay, and four gallons of water is large enough to be representative and small enough to be convenient. Mixing may be readily accomplished in a five gallon bucket or in any convenient mixer. Agita tion should be carried out by means of a convenient agitator. A rotation speed of 1725 rpm. has been selected as being very good. A good propeller to be used for mixing is a 3.1-inch diameter, three-bladed propeller pitched to lift the mix during agitation. Variation in time of mixing has only a minor eifect on a good mineral wool, but can introduce breakdown in fiber lengths of brittle wool. A good standard mixing is 10 minutes which is suflicient to reveal a tendency toward brittleness. The entire dispersion procedure should be carried out so as not to change the fibers any more than necessary consistent with good dispersion. Once a mixing procedure has been chosen, the present method will give good results so long as the adopted mixing procedure is consistently used from sample to sample.

Once dispersed, the dispersion is passed to the testing trough using some means to insure a uniform flow from a fixed starting height. A convenient trough is illustrated at FIG. 2 wherein the walls 1 may be of Wood, metal, or other material, but are preferably made of glass or rigid transparent plastic in order that the thickness and length of the resulting mat may be easily seen. The dispersion enters the mixing trough :through the inlet 2 and passes over the cross 'bafiie 3 which serves to distribute the entering slurry to be tested. The area between the cross bafide 3 andthe wall 1 containing the inlet 2co'nstitutes the head box 4. The wire screen 5 allows the water 'to drain into the chamber 6 from which the white Water flows out the outlet 7.

As the test dispersion flows over the 'cross ba-fiie 3 and down the Wire 5, water immediately begins to drain into the chamber 6 leaving a mat, not shown, on the Wire 5. The volume of this mat, and the length of this mat down the Wire starting from the cross battle 3 are measures of the quality of the mineral wool. The larger thevolume of the mat and the shorter the length of the mat, the higher the 'quality of the mineral wool.

In FIG. 2, a convenient Width of the trough shown is 4 inches and a convenient screen length is 48- inches. Different dimensions may be used, and that volume and mat length may be noted on the different dimensioned trough to determine correlation with good performance on the production "lines.

The length of the mat may easily be determined by marking gradations on one of the side walls 1 of the trough. Transparent walls are preferred. Volume measurements may conveniently be made by using 2-inch increments of length, measuring the volume of each 2-inch increment, and adding incremental volumes to arrive at the total. Any suitable volume-calculating and measuring device may be used. For example, a rod having a fixed area at the bottom thereof may be placed on the top surface of the mat at regular intervals, and the thickness of the mat determined by noting the height of the rod above some fixed point, for example above the top of the Walls. The depth of the m'a-t may be converted into volume per increment by a direct reading scale in order to speedup volume measurement. I

The clay to be used in the present process should be a clay having no swelling properties. Substantially 100% should pass through -a ZOO-mesh screen, U.S. Standard. A kaolinite is "suitable. It should be ebtained lf-rem a source that Will provide a uniform product from bag to bag and from shipment to shipment; uniformity is of prime importance. Specific characteristics of a clay found to be satisfactory '(J-. M. 'H-uber Special Hydratex) are:

Particle size: Percent Residue on 3'25-m'esh screen, maxi-mum Under 2 microns a 77.0-80.0 Above 5 microns a- 3.0-6.0

Chemical composition: Percent SiO 44.0-46.0 A1203 F6203 TiO 1.0-2.0

The following example illustrates several embodiments of the invention.

Example A series of evaluation tests was run on various types of mineral wool obtained 'on the open market. In each instance a half-pound of the mineral Wool sample and a half-pound of J. M. Huber Special Hydratex clay were stirred in 4 gallons of water in a 12-inch diameter, 18-inch deep, conic-a1 bottom tank using an electric motor-driven agitator rotating at 1725 rpm. and having a 3.1-inch diameter, three-bladed :propeller pitched to lift the mix. Mixing time was minutes. At the end of 10 minutes the agitator was turned 01f, the motion of the slurry was stopped by inserting a bafiie into the mixing tank, then the slurry was fed through a l-inch orifice at the bottom of the mixing tank through a line to the head box of the testing trough. The orifice in the tank was 10 inches above the center line of the inlet in the head box. The head box constituted one end of the testing trough, separated -from the drainage Wire by a cross baffie measuring 3 inches in height. The distance from the cross bafile to the end of the head box containing the inlet orifice was 5 /2 inches. Nine specimens of Wool were tested with the following results, three test runs being made on each kind of wool.

Shot Volume Length Sample Content, of Mat of Mat Percent (cu. in.) (inches) 160 -24 A 32. 0 156 24 i i 158 24 173 22 B 35.0 174 23 176 23 I 25 O 40. 4 142 1 25 147 '27 156 25 D 35. 6 157 25% I 91 I 34 F 30. 6 171 25 172 25 157 28 G 42. 0 164 26 161 27 H 37.0 153 30 15s 30 I 149 32 I 37. 8 149 81% The samples identified as C and D were just barely acceptable on the production line, indicating that specifications for acceptable mineral Wool should be drawn requiring the mineral wool to exceed cubic inches in volume and not to exceed 27 inches in the length of 'the mat when evaluated by this test.

The reproducibility of the test using the same equipment under the same conditions described above was determined by using 10 samples of the sample B Wool from the same bag. The following are the results:

Sample ,Volume Length (cubic inches) '(inches) Average Maximum Deviation.

I claim:

1. The method of determining the board-making quality of 'mineral wool which comprises forming a definite quantity of an aqueous dispersion of a clay and the mineral Wool to be tested, passing the dispersion to a head box, passing the dispersion from the head box to a drainage wire adapted to retain the clay and fibers, and measuring the volume and the length of the mat of the retained clay and fibers.

2. The method according to claim 1 wherein the clay and the mineral wool are used in equal amounts by weight.

3. The method according to claim 2 wherein the clay and the mineral wool are used in amounts of one-half pound each. dispersed i114 gallons of water.

5 6 4. Testing apparatus for determining the board-making References Cited by the Examiner quality of mineral wool comprising a trough having four UNITED STATES PATENTS Walls and a bottom, an inlet at one end of said trough, a cross baflie positioned near said inlet, a fixed drainage 2 92 32 df thbtt dt 11 ddtd 1 wire space rom e o om of sa1 roug an a ape 5 2,727,623 12/1955 Beaver 209498 X to retain thereon a mat of mineral wool fibers and clay,

a water runoif chamber formed between the bottom of said trough and said wire, an outlet at the end of said RICHARD QUEISSER Pr'mary Exammer' water runoff chamber opposite from said cross bafile and JOSEPH P. STRIZAK, DAVID SCHONBERG, means on said trough for determining the length of said 10 Examiners.

v mat.

UNITED STATES PATENT OFFICE- CERTIFICATE OF CORRECTION Patent No. 3,222,924 December 14, 1965 Jack E. Gaston that error appears in the above numbered pat- It is hereby certified ent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 22, for "this" read the line 36, for "wood" read wool column 2, line 22, for "from" read form line 62, for "lengths" read length line 63, after "mixing" insert time column 4, in the first table, first column, line 5 thereof, for "E read E in the second table, second column, last line thereof, for 3.4%)" read 6 3.4 0)

Signed and sealed this 9th day of August 1966,

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. THE METHOD OF DETERMINING THE BOARD-MAKING QUALITY OF MINERAL WOOL WHICH COMPRISES FORMING A DEFINITE QUANTITY OF AN AQUEOUS DISPERSION OF A CLAY AND THE MINERAL WOOL TO BE TESTED, PASSING THE DISPERSION TO A HEAD BOX, PASSING THE DISPERSION FROM THE HEAD BOX TO A DRAINAGE WIRE ADAPTED TO RETAIN THE CLAY AND FIBERS, AND MEASURING THE VOLUME AND THE LENGTH OF THE MAT OF THE RETAINED CLAY AND FIBERS. 